1. Field of the Invention
This invention relates to an ice thermal storage medium comprising water and a water-soluble additive.
2. Description of Related Art
The ice thermal storage medium is a material containing water and serves to conduct a heat exchange around a freezing point of the resulting ice. Such an ice thermal storage medium is used in air conditioning, refrigerating, refrigerated storing, quick freezing, ice thermal storing and the like.
As such an ice thermal storage medium is used an aqueous solution added with ethylene glycol. This ice thermal storage medium is used in a dynamic type ice making called as a crystal ice or a liquid ice.
The inventors have found that the ice thermal storage medium using ethylene glycol has an advantage of enabling to continuously make granular ices, but a freezing point of the ice thermal storage medium lowers as an ice packing factor (IPF=a ratio of amount of ice formed to initial amount of aqueous solution) increases. Therefore, it has been confirmed that in order to obtain a higher ice packing factor, a refrigerating machine should be operated at a region of a low coefficient of performance (COP) by reducing an evaporation temperature in the refrigerating machine.